Foreign Currencies and the fluctuating rouble exchange rate
Currency fluctuations
Based on the Central Bank of Russia policy the exchange rate of the rubel to other currencies is not stabilized any more but is allowed to fluctuate. Fluctuations of several percent per day or week have become a normality.
The standard process when an employee requests a refund of e.g. a US Dollar expense, is that he is paid in roubles at the official central bank rate of the date of the expenses report (when processed by the accountant). With high fluctuations of the rouble if the employee needs the reconvert the funds into US Dollar this can result in currency gains or losses.
An employee can also be refunded at a different exchange rate – e.g. at the date of purchase – but this generates additional work. Or a practical solution is when an employee pays a Euro purchase with a rouble credit card he can document the rouble amounts that he paid and request them back from his employer.
The best solution is that it is fixed in a policy how currency matters are addressed. An advise to each employee with very high expenses is to review this with his accountant.
Timing of expenses and its impact on them:
Expenses are often filed substantially after the travel and in the following accounting period. Costs thus often arise in the next period or prior periods must be reopened to book costs into the past. 
In principle it is best is to have a policy where expense reports are filed and processed as soon as possible.
Officially, according to accounting regulations, expense reports must be filled within 3 days after the trip / incurrence of expense. Auditors often comment on this item.
Corporate Credit Cards
Corporate Credit cards can simplify accounting work. Though any usage of the credit card where afterwards expense documentations are not provided are counted as a liability of the employee towards the company and should be closely monitored in order to avoid issues.
Additionally rules should be set on cash withdrawals by such credit cards, though it is best to avoid such withdrawals if at all possible.
Eligibility to file expense reports
Eligible to be refunded expenses as expense reports are only for full time employees, not freelancers (ГПХ). This in practical work creates issues where a work around needs to be agreed on.