Is there any documentation on uploading accruals?
Not sure if I understand the question correctly.
We import Time and Expenses (or alternative ways to capture/enter them). Our Import automatically matches columns to fields, so there is usually no need for a dedicated import format and we de-reference lookups, e.g. user resource email rather the id.
For time off, we generate Time Off Accrual (time available per employee for time off) - or you can import them via the standard Salesforce import options (dataloader, etc.). There is no utility for that, so you need to convert the data to something dataloader can process - i.e. convert e.g. employee numbers to resource ids.
We can also create revenue accruals (i.e. for fixed price projects, the accrued revenue based on completion rate, etc.). But the is an output based on the data entered, not an import/input.
So not sure which accrual you mean.