MosoFin skill · fixed-asset-register-and-depreciation · learning guide

From one new machine to a register that ties both ways

This page shows how the skill keeps a fixed asset register and calculates book depreciation, one level at a time. It starts with one machine in one month. It ends with the things that the skill will not do. The page quotes every rule from the skill and works every number in front of you.

The rules are the skill's ownThe page quotes each rule word for word, with the file and section it comes from.
Outside sources back the factsThey are three sections of OpenStax textbooks, the IFRS standard IAS 16 and two IRS pages. The IRS pages explain the tax side only. Each source has a number and a link.
The page shows the mathOpen "Check it yourself" on any level. Follow every line on a calculator.
Your numbers, your checkAt the end, enter one asset of your own. The page calculates its book charge for a month, and the book gain or loss when you sell it.
Rule: quoted from the skill Fact: from a cited authority, numbered like 1 Example: made-up figures, calculated in full
How it thinks

Ten rules the whole skill runs on

Every level below applies one or more of these rules. The examples use one made-up company, Northbrook Trading, which keeps its books in US dollars under US GAAP. The month is Tuesday 1 September to Wednesday 30 September 2026. The skill reads the QuickBooks Online company "Northbrook Trading" through MosoFin, and the register comes from a spreadsheet that the owner uploaded.

Book and tax

Two depreciation figures, kept apart

A business can have two depreciation figures for the same asset. This page keeps them in separate boxes. Every figure in the levels and the calculator is a book figure.

Book depreciation · the skill calculates it

The skill uses your own policy for each asset class: the useful life, the method, the salvage value and the convention. You give the policy, and the skill applies it. The textbook methods are in source 11.

This figure goes in your financial statements. Levels 1 to 6 and the calculator show only book figures.

Tax depreciation · your tax preparer calculates it

MACRS, section 179, bonus depreciation and the de minimis safe harbor are federal tax rules56. The skill marks tax depreciation [manual], always, and hands it to your tax preparer.

Some owners post the accountant's tax figure as the book figure. Intake question D2 asks this. For those owners, the skill uses the accountant's schedule as the register source and calculates no separate charge.

Learning path

Six levels, from simple to complex

Check it yourself

Put in your own asset

Enter one asset, or load an example. Part 1 runs the Step 3, 4 and 5 formulas from references/method.md. Part 2 runs the Step 8 gain or loss. Every result is a book figure. The page has no tax mode, and it sends nothing anywhere.

Part 1: Depreciate one asset (book)

The asset
Your policy and the month

Straight-line: (cost − salvage) ÷ (life × 12) each month. Double-declining: 2 ÷ life a year, applied to the book value at the start of each year of service, ÷ 12 each month. Both methods stop at salvage. Full month charges the whole first month. Half-month charges half of it. Pro-rata charges the days from the in-service date to the month end. The page shows no disposal month. Your own policy can differ from these choices. Preset A gives $160.00, $160.00 and $19,040.00. Preset B gives $600.00, $23,400.00 and $17,600.00.

Part 2: Sell an asset (book)

The sale
The entry as booked

Tick this box when the entry credits the cost but does not debit accumulated depreciation. That is the half-entry from Level 4.

Book gain or loss = proceeds − (cost − accumulated depreciation). Record the depreciation to the sale date first. The old van preset gives a book value of $0, a gain of $4,000, a booked loss of $26,000 and an error of $30,000. An entry from this page is a proposal. A person decides whether to post it.

Using it

What it asks, needs and gives back

Asks firstA: Use MosoFin for this run, or upload the data yourself? It asks this only when the MosoFin tools are present. B: Which period? C: Your existing asset register, if you have one. D: The useful life, method and salvage policy for each class. D2: Do you book depreciation by your own policy, or post the figure from your tax return or accountant? E: Your capitalization threshold. F: Your convention for the first and last month. G: US GAAP, IFRS or local GAAP? H: Which tax jurisdiction? I: Any impairment triggering events, and when did someone last count the assets, and who?
NeedsThe skill needs the trial balance or balance sheet and the GL detail for the asset accounts. With MosoFin, it reads both. The skill also recommends the register, the expense-account detail and the purchase invoices. Without a register, the skill offers a draft register from the GL, and you approve it or change it.
Gives backThe skill gives back eleven sheets: register, schedule, acquisitions, disposals, roll-forward, tie-out, impairment, proposed entries, tax-book differences, threshold scan and coverage. It asks before it makes an Excel file.
NeverThe skill never uses MosoFin before you agree. It reads nothing before you answer its questions and say yes to its read-back. It never writes to any system, and it never defaults a life, salvage, threshold or convention. It reports candidates, never conclusions. A clean tie-out never replaces the physical count.
Sources

Where every fact on this page comes from

The rules are the skill's own. The facts below come from six outside sources. They are three sections of OpenStax textbooks, the IFRS standard IAS 16 and two IRS pages. Sources 5 and 6 explain the tax side only, and the skill does not apply them. MosoFin checked each one on 28 October 2026 from search results and did not open the pages. Follow the link for today's wording.

    Not backed by an outside authority. The 29 edge cases, the threshold scan, the implied-rate check, the two-way tie-out and the eleven sheets are the skill's own. So are the [auto], [gated] and [manual] verdicts. MosoFin made up Northbrook Trading, its assets, its policies and every figure in the examples. The page marks them where they appear.