Nobody joins an engineering or architecture firm to fill out timesheets. They still matter more than almost any other piece of admin, because hourly work can't be billed until the hours are entered and approved. When a timesheet is two weeks late, every invoice that depends on it is late too.
Make it weekly
Time is easiest to remember the same week it happened. Monthly timesheets turn into reconstructions from calendars and sent mail, and the hours that get forgotten are hours that never get billed. A weekly rhythm keeps entries accurate and keeps billing moving.
Pick one deadline and keep it
A fixed deadline, like noon on Monday for the previous week, is easier to follow than "sometime soon." It also gives project managers a predictable time to review.
Tie every entry to a project and phase
An entry that just says "project work" can't be billed against a phased contract. Entries should name the project and the phase or task, so approved time lands on the right line of the right invoice.
Approve quickly
Approval is where a project manager confirms the hours belong on the project and are billable. If approvals wait until month end, so does billing. A short weekly review of each project's time keeps both current.
Keep rates in one place
Billing rates change: raises, new roles, a new rate table for a new client. If rates live in personal spreadsheets, invoices end up using whichever version someone opened. Rates with start dates, kept in one place, mean each entry is billed at the rate that applied when the work was done.
Log expenses the same week
Mileage, printing, and permit fees are easy to lose. Logging them with the week's time, with receipts in hand, keeps them billable.
How Kineo handles it
Kineo uses a weekly timesheet. People submit their week, and project managers approve it. Approval locks in the value at the rate in effect for that work, so a later rate change doesn't rewrite approved hours. Rates live in rate tables with start and end dates, with overrides for individual projects.
Expenses are entered with their markup, and approved time and expenses feed straight into the contract's invoices. If someone keeps notes on their week, they can ask the assistant to enter the time from those notes and review the entries before submitting.